A switch unit in which a printed-circuit board and the like are accommodated employs a structure into which water hardly permeates since it is necessary to prevent water from permeating into the switch unit.
For example, a switch unit disclosed in Patent Document 1 has a structure that includes a lower case and an upper case fitted to the lower case from above. A printed-circuit board and the like are accommodated in the lower case, and operation portions of switches are provided at an upper portion of the upper case. Protruding portions formed on the side surfaces of the lower case are engaged with engaging holes formed at the side surfaces of the upper case, so that the upper case and the lower case are integrated with each other. Here, in order to prevent water from permeating from the engaging holes of the upper case, ribs are formed on the side surfaces of the upper case so as to surround upper portions and side portions of the engaging holes and guide water droplets and the like, which trickle down the side surfaces of the upper case from above, so that the water droplets flow down along the outsides of the ribs and the like.